add_codecov_badge (#1172)

Signed-off-by: Pablo Garay <[email protected]>

Author: pablo-garay

README.md

@@ -1,6 +1,7 @@
 <div align="center">
 
   <a href="https://github.com/NVIDIA-NeMo/Curator/blob/main/LICENSE">![https://pypi.org/project/nemo-curator](https://img.shields.io/github/license/NVIDIA-NeMo/Curator)</a>
+  <a href="https://codecov.io/github/NVIDIA-NeMo/Curator">![codecov](https://codecov.io/github/NVIDIA-NeMo/Curator/graph/badge.svg)</a>
   <a href="https://pypi.org/project/nemo-curator/">![https://pypi.org/project/nemo-curator/](https://img.shields.io/pypi/pyversions/nemo-curator.svg)</a>
   <a href="https://github.com/NVIDIA-NeMo/Curator/graphs/contributors">![NVIDIA-NeMo/Curator](https://img.shields.io/github/contributors/NVIDIA-NeMo/Curator)</a>
   <a href="https://github.com/NVIDIA-NeMo/Curator/releases">![https://github.com/NVIDIA-NeMo/Curator/releases](https://img.shields.io/github/release/NVIDIA-NeMo/Curator)</a>